This article is oriented on application of dense gases as alternative reaction media for enzyme-catalyzed reactions. The main factors influencing enzyme stability (water activity, pressure, temperature, pressurization/depressurization) and the influence of process parameters on the initial reaction rates and productivity are presented. An overview of the research in the field of enzymatic reactions in dense fluids is shown. (c) 2005 Elsevier B.V. All rights reserved.